The servers have different IPs, and domains.
Therefore, to any mail provider, they are different things... and even when SL is treated normally, there is no guarantee LOB will, and the funny thing is: some mail servers from yahoo.com work, some don't... Oo pretty randomly.
as for the other big ones, I mailed a few to let your mails go through.
Hotmail accepted them, I think they might forward them soon.